Field of the Invention
The present invention relates to a toner to be used in an image forming method involving using an electrophotographic system such as a copying machine, a printer, a facsimile, or a composite machine thereof, and to a method of producing the toner.
Description of the Related Art
In recent years, an image forming apparatus such as an electrophotographic copying machine, which has heretofore merely copied an original, has become widely available as an information output device linked to any other information device in countries all over the world because of its digitization. Accordingly, the number of abilities that a toner is required to have such as high definition, high quality, high image quality, a high speed, and high reliability does not cease to increase. In particular, the toner has been required to provide stable image quality independent of an environment because the variety of environments where the toner is used has expanded in association with market expansion.
For example, it has been known that the chargeability of an electrophotographic toner reduces under a high-humidity environment, and image quality is impaired by an influence of the reduction in some cases. The impairment is specifically, for example, the occurrence of fogging in which the toner is slightly developed in a white portion (non-printing portion) where nothing is intended to be printed, and hence the toner appears like greasing. In addition, when the flowability of the electrophotographic toner reduces, the property by which a developer is supplied is impaired, and hence the image quality is impaired by an influence of the impairment in some cases. For example, when a high-density image is repeatedly output, a density reduces on the rear end side of the image.
Further, from the viewpoint of energy savings by a reduction in power consumption, a mainstream fixing system in an image forming apparatus has started to shift from a conventional hard roller-type system having a large heat capacity to a light-pressure fixing system such as film fixation or belt fixation having a small heat capacity. In the light-pressure fixing system, a reduction in heat capacity of a fixing member has been performed in order to shorten a time period required to reach a fixation set temperature (control temperature), thereby achieving a system that is excellent in quick start property. Because of the reduction in heat capacity of the fixing member, the extent to which the temperature of the fixing member reduces when high-speed continuous copying is performed enlarges as compared with the conventional hard roller-type system. Accordingly, a toner that can be fixed at additionally low temperature is needed, and hence not only an additional improvement in low-temperature fixability but also a wide fixation temperature width (hereinafter sometimes referred to as “fixation latitude”) has started to be required as performance that the toner is desired to have.
To satisfy the requirement, a high-flowability toner having high charging stability against a change in hygrothermal environment, i.e., high charging stability against an environment, and having a wide fixation latitude has started to be required more than ever before, and hence various attempts have been proposed. Japanese Patent Application Laid-Open No. 2005-195934 proposes the use of a polyolefin resin having a cyclic structure as the binder resin of a toner. The polyolefin resin having a cyclic structure is colorless and transparent, has a high light transmittance, and has a low moisture absorbing property. Japanese Patent Application Laid-Open No. 2005-195934 describes that when a silicone resin or a fluorine resin is further incorporated into the toner containing the polyolefin resin having a cyclic structure as its binder resin, an electrophotographic color toner excellent in charging stability against an environment, having high color developability, and excellent in low-temperature fixability and flowability can be provided.